Kampen and Zwolle are vulnerable when a northwesterly storm arises during high tide in the IJssel. There is now a creative idea to increase the safety of both Hanseatic cities: transforming the IJssel estuary into a kind of Biesbosch.
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The Kampen city front is one of the most famous cityscapes in our country. The grand houses, an old city gate and various church towers make the IJsselkade a picture. Yet there is a danger lurking for the historic Hanseatic city, due to its location in the estuary of the IJssel. If a combination of circumstances occurs, Kampen could find itself in dire straits, says Bert Bijkerk, strategic director at the Drents Overijsselse Delta water board.
Kampen is located right along the river. When the IJssel overflows its banks, the high-water brigade comes to the rescue. This is a volunteer group from the water board that installs a mobile flood barrier on the IJsselkade in a few hours, consisting of 200 aluminum bulkhead beams. “A safe solution for now, but in the long term Kampen will remain vulnerable, especially if the water level in the IJsselmeer rises under the influence of sea level rise. This also applies to a lesser extent to Zwolle,” says Bijkerk.
The dangerous cocktail begins when a funnel forms in the mouth of the nearby Ketelmeer in which extreme water levels from the IJsselmeer occur up to 3 meters above NAP during a northwesterly storm. If the IJssel also has a high discharge, Kampen will be in trouble. This would create a dangerous backwater on the IJssel and the city could be flooded.
“To protect Kampen in the future, a higher flood defense is actually necessary. But that would seriously affect the appearance of the beautiful city front and no one wants that. Many dikes in the IJssel-Vecht delta also need to be strengthened due to stricter requirements for water safety,” says Bijkerk. That is why he looked for a creative water management solution that would serve the beautiful Hanseatic city. He found it in the nearby Ketelmeer.
The Ketelmeer is both a river and a lake
The Ketelmeer forms the connection between the IJssel and the IJsselmeer. It is wedged between the Noordoostpolder and Flevoland. The name of the 3,500 hectare lake refers to a depth in the ground (cauldron). Bert Bijkerk does not have to search long for a characterization of this pond. “It is a tightly defined, ugly body of water with steep banks, where there is no fun to be had. An exception is the eastern part where there are already some islands with shallows.”
Bijkerk takes out a map of the area. “Look, you see that the mouth of the IJssel with high river discharge is in fact not near Kampen, but near the Ketelbrug. The Ketelmeer is therefore both a lake and a river and therefore part of the IJssel-Vecht delta. You can use it smartly to make.”
Before Bert Bijkerk continues, he points to a dredger on the IJssel near Kampen. A floating crane machine scrapes the bottom of the river to bring up sand and sludge. The stuff is dumped into the hold of a flat-bottomed boat. “The IJssel carries a lot of sand and sediment. This is now sinking to the bottom near Kampen due to a summer bed lowering of 2 meters. This blocks the supply of sediment to the Ketelmeer. If you restore and embrace that, the Ketelmeer will automatically turn into a shallow delta. If we lend a helping hand, we can accelerate this process. That is good for water safety and for nature.”
The Ketelmeer could be transformed into a shallow river delta with dozens of channels and nature islands, and with a channel for shipping. Photo: Anne Blaak
Keteldelta, that is the name of the ingenious concept of which Bijkerk calls himself the spiritual father. “Simply put, it means that we are transforming the Ketelmeer into a shallow river delta with dozens of channels and nature islands, with a channel for shipping. With this system measure we find an answer to various challenges and tasks for the IJssel-Vecht delta. “
The water safety expert from the water board receives support from Lilian Hermens, rivers program manager at Staatsbosbeheer. She is working on the assignment to develop more nature in the IJssel-Vecht delta. “The central government has an ambition to create 8,300 hectares of new nature in the estuary of the IJssel and the Vecht. If you want to do all of that on land, it will result in a huge battle over lack of space and farmers’ land. When If you also create that new nature in the water, it cuts both ways.”
Hermens is working on the Programmatic Approach to Large Waters (PAGW) on behalf of two ministries. The aim is to restore large-scale wet nature and improve ecological water quality in four places in the country by 2050: along the Maas, in the Biesbosch, Gelderse Poort and in the estuary of the Vecht and the IJssel.
“These are robust and resilient nature reserves with viable populations of animal species that are currently having a hard time, such as the bittern, great reed warbler, night heron and otter. We are thinking of reed marshes, shallow riparian zones, flood plains and riparian forests, with which we can cope with climate change.”
This ambition fits in seamlessly with Bert Bijkerk’s idea for the Ketelmeer. “If we create a few thousand hectares of shallow nature from the Ketelbrug. Starting south of Urk and then in the Ketelmeer. This will benefit Kampen’s water safety, because the islands form a natural brake for rising water from the IJsselmeer. Moreover, Fewer higher dikes are needed around the Ketelmeer, because wave action is decreasing.”
Agriculture can then remain on Kampereiland
Another advantage of Keteldelta is that agriculture on Kampereiland can continue to exist. The Kampereiland is an old river siltation, created by islands that grew together in the mouth of the IJssel. Farmers settled on these heights in the 15th century. The meadows on Kampereiland are nationally known for their excellent quality hay.
Over the course of recent history, many green planners have had their eyes on Kampereiland. But the municipality of Kampen – owner of the area – would like to maintain the peasantry in this culturally and historically valuable river landscape. “We can leave Kampereiland out of all plans if we develop the Keteldelta. This way we don’t have to sacrifice good agricultural land,” says Bijkerk.
He lists another advantage: the new nature in the Ketel Delta can easily move with changing water levels in the IJsselmeer. The level of the IJsselmeer is expected to rise in the future due to climate change. “The IJsselmeer area is also known as the national rain barrel. It is the freshwater supply for a large part of the Northern Netherlands. Farmers and drinking water companies depend on fresh IJsselmeer water.”
Drinking water company Vitens has plans to extract drinking water from the Ketelmeer. According to water safety specialist Bijkerk, this is not at odds with the Keteldelta concept. “We can set up reservoirs for drinking water extraction.” The inland shipping route on the IJssel to the IJsselmeer can also continue to exist.
By transforming the Ketelmeer into a shallow delta, it becomes part of the IJssel river system. “We are, as it were, stretching the IJssel a few kilometers,” says the Staatsbosbeheer program manager. “This can create a fantastically large area à la the Biesbosch, with reed marshes, riparian forests and sandbanks and open water. The more nature we create, the more we improve the water quality. And the more is possible for recreation and water sports. Of course you have to We must carefully consider where this is desirable. Because a breeding white-tailed eagle does not go well with a boat with bathers nearby.” 250,000 euros has been allocated for further research into the feasibility of Keteldelta.